In cellular communication in which radio base station devices and radio terminal devices communicate with each other, radio relay station devices that perform amplification and relay are used in some cases. Hereinafter, a radio base station device, a radio terminal device, and a radio relay station device may be referred to as a “base station”, a “terminal”, and a “relay station”, respectively. A relay station amplifies a signal transmitted from one of a base station and a terminal, and relays the signal to the other. This makes it possible to increase communication quality by improving reception quality. For this reason, by densely arranging a plurality of relay stations within the “communication area” of a base station, the communication quality of the entire communication area is expected to be improved. Note that the “communication area” is an area at which radio waves transmitted from a base station arrive with a power equal to or larger than a predetermined value.
However, when a plurality of relay stations existing within the communication area of a base station perform transmission (relaying) using the same frequency, that is, when relay stations are of a full-duplex type, there are some cases where a signal transmitted (relayed) by a first relay station is received by a second relay station. Then, the received signal may be transmitted (relayed) by the second relay station, and thereafter be received by the first relay station. That is, a signal on which relay processing is repeatedly performed by a plurality of relay stations will be received with a large delay by a receiving device, which is a base station or a terminal. Such a signal with a large delay is likely to cause large interference in the receiving device. Additionally, since relay processing is repeatedly performed, there is a possibility that the power value of a signal input to an amplifier of a relay station exceeds a value assumed at the design phase, which, in turn, causes an amplifier to oscillate.
To avoid such a problem, a technique has been proposed for stopping relay processing of some of a plurality of relay stations included within a communication area, based on each propagation attenuation (that is, path loss) between a relay station and a terminal.
“Area Power Consumption in a Single Cell Assisted by Relays” in Proc. IEEE/ACM Int. Conf. Green Computing and Communications (GreenCom) & Int. Conf. Physical and Social Computing (CPSCom), December 2010, pp. 460-465 discloses an example of the related art.